Genetic and familial environmental effects on suicide--an adoption study of siblings

A population-wide analysis of the familial risk of suicide in Utah, USA

BACKGROUND

The degree to which suicide risk aggregates in US families is unknown. The authors aimed to determine the familial risk of suicide in Utah, and tested whether familial risk varies based on the characteristics of the suicides and their relatives.

METHODS

A population-based sample of 12 160 suicides from 1904 to 2014 were identified from the Utah Population Database and matched 1:5 to controls based on sex and age using at-risk sampling. All first through third- and fifth-degree relatives of suicide probands and controls were identified (N = 13 480 122). The familial risk of suicide was estimated based on hazard ratios (HR) from an unsupervised Cox regression model in a unified framework. Moderation by sex of the proband or relative and age of the proband at time of suicide (<25 v. ⩾25 years) was examined.

RESULTS

Significantly elevated HRs were observed in first- (HR 3.45; 95% CI 3.12-3.82) through fifth-degree relatives (HR 1.07; 95% CI 1.02-1.12) of suicide probands. Among first-degree relatives of female suicide probands, the HR of suicide was 6.99 (95% CI 3.99-12.25) in mothers, 6.39 in sisters (95% CI 3.78-10.82), and 5.65 (95% CI 3.38-9.44) in daughters. The HR in first-degree relatives of suicide probands under 25 years at death was 4.29 (95% CI 3.49-5.26).

CONCLUSIONS

Elevated familial suicide risk in relatives of female and younger suicide probands suggests that there are unique risk groups to which prevention efforts should be directed - namely suicidal young adults and women with a strong family history of suicide.

Genetic liability to suicide attempt, suicide death, and psychiatric and substance use disorders on the risk for suicide attempt and suicide death: a Swedish national study

BACKGROUND

How does genetic liability to suicide attempt (SA), suicide death (SD), major depression (MD), bipolar disorder (BD), schizophrenia (SZ), alcohol use disorder (AUD), and drug use disorder (DUD) impact on risk for SA and SD?

METHODS

In the Swedish general population born 1932-1995 and followed through 2017 (n = 7 661 519), we calculate family genetic risk scores (FGRS) for SA, SD, MD, BD, SZ, AUD, and DUD. Registration for SA and SD was assessed from Swedish national registers.

RESULTS

In univariate and multivariate models predicting SA, FGRS were highest for SA, AUD, DUD, and MD. In univariate models predicting SD, the strongest FGRS were AUD, DUD, SA, and SD. In multivariate models, the FGRS for SA and AUD were higher in predicting SA while the FGRS for SD, BD, and SZ were higher in predicting SD. Higher FGRS for all disorders significantly predicted both younger age at first SA and frequency of attempts. For SD, higher FGRS for MD, AUD, and SD predicted later age at SD. Mediation of FGRS effects on SA and SD was more pronounced for SD than SA, strongest for AUD, DUD, and SZ FGRS and weakest for MD.

CONCLUSIONS

FGRS for both SA and SD and for our five psychiatric disorders impact on risk for SA and SD in a complex manner. While some of the impact of genetic risk factors for psychiatric disorders on risk for SA and SD is mediated through developing the disorders, these risks also predispose directly to suicidal behaviors.

The Sources of Parent-Child Transmission of Risk for Suicide Attempt and Deaths by Suicide in Swedish National Samples

OBJECTIVE

The authors aimed to clarify the sources of parent-child transmission for suicide attempt and death by suicide.

METHODS

Three sources of parent-child resemblance (genes plus rearing, genes only, and rearing only) were examined in parents and offspring from four family types from Swedish national samples: intact nuclear families, families with a not-lived-with biological father, families with a stepfather, and adoptees and their biological and adoptive parents. Parent-child resemblance was assessed primarily by tetrachoric correlation.

RESULTS

For suicide attempt to suicide attempt transmission, best-estimate tetrachoric correlations for genes plus rearing, genes only, and rearing only were 0.23 (95% CI=0.23, 0.24), 0.13 (95% CI=0.11, 0.15), and 0.14 (95% CI=0.11, 0.16), respectively. Suicide attempt was more strongly transmitted to male offspring compared with female offspring. Parental psychiatric disorders accounted for 40% of the genetic transmission but had no impact on rearing effects. For suicide death to suicide death transmission, best estimates of tetrachoric correlations for genes plus rearing, genes only, and rearing only were 0.16 (95% CI=0.15, 0.18), 0.07 (95% CI=0.02, 0.12), and -0.05 (95% CI=-0.17, 0.07), respectively. Although the suicide attempt-suicide death genetic correlation was high (0.84), the hypothesis that they reflect behaviors only differing in severity on the same continuum of genetic liability could be rejected.

CONCLUSIONS

The transmission of suicide attempt across generations is moderately strong and arises equally from genetic and rearing effects. Parental psychiatric illness explains almost half of the genetic transmission of suicide attempt but none of the rearing effect. Suicide death is modestly transmitted across generations, probably via genetic effects, although rearing may play a role. While suicide attempt and suicide death share a substantial proportion of their hereditary risk, they do not, from a genetic perspective, simply reflect milder and more severe forms of the same diathesis.

Alcohol Use Disorder and Risk of Suicide in a Swedish Population-Based Cohort

OBJECTIVE

The authors examined the association between alcohol use disorder (AUD) and risk of suicide, before and after accounting for psychiatric comorbidity, and assessed the extent to which the observed association is due to a potentially causal mechanism or genetic and familial environmental confounding factors that increase risk for both.

METHODS

Longitudinal population-wide Swedish medical, criminal, and pharmacy registries were used to evaluate the risk of death by suicide as a function of AUD history. Analyses employed prospective cohort and co-relative designs, including data on 2,229,880 native Swedes born between 1950 and 1970 and observed from age 15 until 2012.

RESULTS

The lifetime rate of suicide during the observation period was 3.54% for women and 3.94% for men with AUD, compared with 0.29% and 0.76% of women and men, respectively, without AUD. In adjusted analyses, AUD remained robustly associated with suicide: hazard ratios across observation periods ranged from 2.61 to 128.0 among women and from 2.44 to 28.0 among men. Co-relative analyses indicated that familial confounding accounted for some, but not all, of the observed association. A substantial and potentially causal relationship remained after accounting for a history of other psychiatric diagnoses.

CONCLUSIONS

AUD is a potent risk factor for suicide, with a substantial association persisting after accounting for confounding factors. These findings underscore the impact of AUD on suicide risk, even in the context of other mental illness, and implicate the time frame shortly after a medical or criminal AUD registration as critical for efforts to reduce alcohol-related suicide.

Identification of gene ontology and pathways implicated in suicide behavior: Systematic review and enrichment analysis of GWAS studies

Multiple large-scale studies such as genome-wide association studies (GWAS) have been performed to identify genetic contributors to suicidal behaviors (SB). We aimed to summarize and analyze the information obtained in SB GWAS, to explore the biological process gene ontology (GO) of genes associated with SB from GWAS, and to determine the possible implications of the genes associated with SB in Kyoto encyclopedias of genes and genomes (KEGG) biological pathways. The articles included in the analysis were obtained from PubMed and Scopus databases. Enrichment analyses were performed in Enrichr to evaluate the KEGG pathways and GO of the genes associated with SB of GWAS. The findings of biological process GO analysis showed 924 GO involved in genes related with SB; of those, the regulation of glucose import in response to insulin stimulus, regulation of protein localization to plasma membrane, positive regulation of endopeptidase activity, heterotypic cell-cell adhesion, regulation of cardiac muscle cell contraction, positive regulation of protein localization to plasma membrane, and positive regulation of protein localization to cell periphery biological process GO showed significant statistical association. Furthermore, we obtained 130 KEGG pathways involved in genes related with SB, which Aldosterone synthesis and secretion, Rap1 signaling pathway and arrhythmogenic right ventricular cardiomyopathy pathways showed a significant statistical association. These findings give a better perspective of the biological participation of genes associated with SB, which will be important to perform adequate strategies to prevent and treat SB.

Family history of suicide and high motor impulsivity distinguish suicide attempters from suicide ideators among college students

Suicide in college students has become an important public health issue in China. The aim of this study was to identify the differences between suicide attempters and suicide ideators based on a cross-sectional survey. Our results indicate that although female gender, positive screening for psychiatric illness, positive family history of suicide, elevated overall impulsivity, and elevated motor impulsivity were correlated with suicidal ideation, only positive family history of suicide and high motor impulsivity could differentiate suicide attempters from suicidal ideators. Future research with a longitudinal and prospective study design should be conducted to confirm these findings.

Neurotrophin Genes and Antidepressant-Worsening Suicidal Ideation: A Prospective Case-Control Study

BACKGROUND

Antidepressant-worsening suicidal ideation is a rare but serious phenomenon. This study aimed to test for association between antidepressant-worsening suicidal ideation and polymorphisms of BDNF/NTRK2 neurotrophin pathway genes, known to be involved in depression and suicide.

METHODS

This was a case-control study comparing patients with antidepressant-worsening suicidal ideation to patients without. Patients were collected from the GENESE cohort (3771 depressed tianeptine-treated outpatients). Antidepressant-worsening suicidal ideation was defined by an increase of at least 2 points on the Montgomery-Åsberg Depression Rating Scale-item10 during treatment. Controls were matched for age, sex, and baseline Montgomery-Åsberg Depression Rating Scale-item10 score. Thirteen single nucleotide polymorphisms covering 5 BDNF/NTRK2 pathway genes were genotyped.

RESULTS

A total 78 cases and 312 controls were included. Two NTRK2 single nucleotide polymorphisms were associated to antidepressant-worsening suicidal ideation: rs1439050 (P=.01) and rs1867283 (P=.04). Association with rs1439050 remained significant after adjustment for potentially confounding factors, including previous suicide attempts (P<.01).

CONCLUSIONS

This naturalistic prospective study is consistent with previous studies on highlighting the potential role of the neurotrophin pathway, and especially of NTRK2, in antidepressant-worsening suicidal ideation.

Suicidal Behavior in Relatives or Associates Moderates the Strength of Common Risk Factors for Suicide

The prevalence and odds ratios of different suicide risk factors were compared in three pairs of decedents: 80 suicides and 25 injury decedents with blood relatives with suicidal behavior history (biologically exposed); 259 suicides and 126 injury decedents with unrelated acquaintances with suicidal behavior history (socially exposed); and 471 suicides and 523 injury decedents with neither relatives nor acquaintances with suicidal behavior history (unexposed). Negative life events and high psychological stress were more common in socially exposed suicides than in other suicides. The adjusted odds ratios of most established suicide risk factors were higher in unexposed decedents than in biologically or socially exposed decedents, suggesting that the predictive value of established risk factors wanes in individuals who have been exposed to suicidal behavior in family or friends.

Genetic and familial environmental effects on suicide attempts: a study of Danish adoptees and their biological and adoptive siblings

OBJECTIVES

Genetic factors have been found to influence the risk of suicide. It is less clear if this also applies to attempted suicide. We have investigated genetic and familial environmental factors by studying the occurrence of suicide attempts in biological and adoptive siblings of adoptees who attempted suicide compared to siblings of adoptees with no suicide attempts.

METHOD

We used a random sample of 1933 adoptees from the Danish Adoption Register, a register of non-familial adoptions of Danish children, i.e. the adoptive parents are biologically unrelated to the adoptee. Analyses were conducted on incidence rates of attempted suicide in biological and adoptive siblings given occurrence of attempted suicide in the adoptees while also taking into account psychiatric disorders. Information about suicidal attempt and history of psychiatric disorder was based on hospital admissions.

RESULTS

The rate of attempted suicide in full siblings of adoptees who attempted suicide before age 60 years was higher than in full siblings of adoptees who had not attempted suicide (incidence rate ratios (IRR)=3.45; 95% confidence interval [CI]=0.94-12.7). After adjustment for history of psychiatric admission of siblings the increased rate was statistically significant (IRR=3.88; 95% CI-1.42-10.6).

LIMITATIONS

Information on attempted suicide and psychiatric history was limited to that which involved hospitalisation.

CONCLUSIONS

Genetic factors influence risk of suicide attempts.